## College Algebra 7th Edition

$\left\{x|x \ne 2, x\ne -1\right\}$
Factor the trinomial in the denominator to obtain: $=\dfrac{x^2+1}{(x-2)(x+1)}$ The denominator of a rational expression is not allowed to be equal to zero as it makes the rational expression undefined. Note that when x=2 or x=-1, the denominator will be equal to 0. Thus, the domain of the expression is any real number except $2$ and $-1$.